For discussion of the issues faced when building a model or layout - how to replicate wood, what glues to use, exactly how much weathering can a Gnat take, a good source of detailing accessories - you get the picture, I'm sure.

If you're out and about and you see something you think will work for your modelling scale...but you've forgotten your ruler,Here's a site that automatically detects your Phone or Tablet Screen Size and gives you an image of a ruler that can be used in Centimeters or Inches

There's also a (paid) iOS app called Move to measure - flying ruler that measures the distance between two points a few meters apart - you just move your device from one point to the other and it measures how far apart the points are by looking at the device's inertial sensors. This can potentially replace a tape measure. Unfortunately I found the measurements inconsistent.